the fiber ones are somewhat reusable, plastic ones really aren't.. airgas gives me a new one with a tank exchange so i replace it everytime i take the regulator off.

I always thought it was the fiber ones that were one time usage and plastic worked many times. I figured the fiber crushed and was no longer good. Not really sure on that however as my main reg has a built in Quad ring so I don't use any other gaskets.

Anyway those washers are cheap or free with gas so might as well get new ones each time.